The invention relates to a heater strip for use as a heating element in an electric heater or heating module, made as a profiled strip from a flat metallic material forming a resistor section and a plurality of mounting elements for mounting the heater strip to a support or base body, said mounting elements extending over one common longitudinal side of said resistor section and being made as one piece with the resistor section from the flat metallic material.
The invention also relates to an electric heater or heater module, especially also for use for electric heating panels and in particular for glass-ceramic panels, said heater including a base body made of an electrically conductive material and a heater strip provided upright on one surface side of the base body and made of a metallic strip material or starting material, which (heater strip) forms a strip-shaped resistor section that can be energized with a heating current and is fastened to the base body with mounting elements likewise made of the flat strip material and protruding over one common longitudinal side of the resistor section.
The invention further relates to a method for manufacturing the heater strip.
Electric heaters, especially for use for electric heating panels, in particular for glass-ceramic panels, are known in a wide variety of designs. Also known in the art (EP 0 590 315) is the use of a thin flat heater strip as an electric heating element that is energized with the heating current, which (heater strip) is fastened by means of molded mounting plate or elements on one surface side of a support or base body made of an electrically and thermally insulating material, i.e. oriented perpendicular or approximately perpendicular to the plane of the surface side of the base body. The heater strip is manufactured as one piece with the mounting elements from a starting material consisting of thin strip-shaped sheet metal that is suitable for heating elements, so that the mounting elements protrude over one common longitudinal side of a strip-shaped resistor section of the heater strip extending along the entire length of the heater strip. The strip is manufactured by suitable cutting of the strip-shaped starting material on one longitudinal side so that the mounting elements are retained or cut free during cutting. Afterwards, the heater strip is permanently shaped so that the longitudinal extension is sinusoidal. The majority of the successive mounting elements in the progression of the heater strip are located on at least one bend area of the undulation and therefore have a profile corresponding to the bend areas.
The known heater strip is characterized by considerable disadvantages. For example, the mounting elements are provided in the progression of the heater strip at relatively large intervals, in order to compensate for mechanical tensions during operation of the heater through elastic deformation of the heater strip resulting from different longitudinal expansion of the material of the base body and of the heater strip, which without compensation can result in damage to the base body and in particular also in separation of the heater strip from the base body.
A further disadvantage of the known heater strip is that during operation of the heater, successive sections along the heater strip have different temperatures, which can cause, for example, a perceptibly non-homogenous visual glow pattern of the heater strip. Furthermore, the areas of differing temperatures cause additional tensions in the heater strip. In addition, at a given heat output, the areas with a higher temperature are characterized by increased corrosion or oxidation, thus significantly reducing the overall service life of the heater or heating module.
An object of the invention is to provide for a heater strip that eliminates the disadvantages of the existing art, in particular ensuring an even visual heating pattern during operation of the heater, with increased service life and minimization of thermal tensions caused by differing thermal expansion.